GB2064228A - Improvements in motor- immersed fuel pumps - Google Patents

Abstract

The copper wire for the armature coil (14) of a motor-immersed fuel pump for use in the fuel supply system of a vehicle, the brush lead wires (19) if they are made of copper, and likewise the connection leads (20, 21) are coated with a petrol-proof material, such as epoxy resin or other organic adhesive. This prevents the petrol having any contact with copper which would degrade or breakdown the petrol which would itself deteriorate on exposure to petrol. This is particularly advantageous in the case wherein alcohol is added to the petrol, (so-called gasohol). The commutator may be coated with silver. Tin, nickel, silver, aluminum or stainless steel brush leads are suggested. <IMAGE>

Description

SPECIFICATION Improvements in motor-immersed fuel pumps The present invention relates to a motorimmersed fuel pump.

A motor-immersed fuel pump is one pump in which the motor is completely immersed in the flow of fuel being pumped, e.g. in the fuel supply line of a vehicle such as an automoble. This type of fuel pump is advantageous because the heat generated within the motor is carried away to avoid overheating and sparks generated between the commutator and the brushes are suppressed, thereby avoiding explosion of vaporized fuel.

However, petrol is commonly used as a fuel for this type of fuel pumps and petrol becomes degraded by direct contact with copper. On the other hand, pump components containing copper or copper alloy are corroded by petrol. Thus, the degraded petrol would significantly lower combustion efficiency of the internal combustion engine and the service life of the pump would be shortened.

Therefore, it is important that components of a motor-immersed fuel pump should as far as possible be made from a material which does not contain copper or copper alloy, in order to avoid deterioration of the fuel. However, some components do require the use of copper or copper alloy for various reasons including electrical conductivity, mechanical workability, and economic advantage. For example, it is preferable to use copper or copper alloy for such components as commutator segments, an armature coil, and brush and terminal lead wires.

It is true that enamel-coated wire can be used for an armature coil, but when the coil is connected to a commutator segment by soldering or fusing, a significant amount of heat is applied to the connection, which, in turn, melts away a part of the enamel coating to expose the corresponding copper wire. Accordingly, there is formed a copper exposed portion which will come into direct contact with the fuel.

In particular, where use is made of so-called gasohol, which is petrol with added alcohol and which has recently become very popular as one way to curb energy resource problems in future, the corrosive effect of copper-contained components increases tremendously. Accordingly, if there is a copper exposed portion at a connection between the armature coil and commutator segments, the coil could be disconnected from the commutator after few hours of service due to heavy corrosion by gasohol. In such event, the whole pump unit must be dismounted for replacement or repair.

One object of the present invention is to provide a motor-immersed fuel pump which does not cause deterioration of fuel passing therethrough.

Another object of the present invention is to provide a motor-immersed fuel pump which has a structure to prevent its components from corrosion by fuel thereby ensuring a long service life.

Further object of the present invention is to provide a motor-immersed fuel pump which is high in performance and low in price and yet which can be used with alcohol added petrol, socalled gasohol, without problems.

The present invention resides in a fuel pump comprising a motor having casing around the inner surface of which is disposed a plurality of magnets, an armature disposed inside said casing and a driving shaft rotatably supported in the pump and carrying said armature and a commutator, and a pump mechanism driven by said driving shaft and disposed so that the flow path of the pumped fuel is through the casing, the armature thereby being completely immersed in the fuel, the armature coil of said armature comprising a copper wire and a protective layer provided to cover said copper wire, said protective layer being made from a material non-reactive with fuel.

The present invention is further described, by way of example, with reference in the drawings, in which Fig. 1 is a longitudinal section of an immersedmotor fuel pump; Fig. 2 is a cross section of the fuel pump along A-A line of Fig. 1; Fig. 3 is a cross section of the fuel pump along B-B line of Fig. 1; and Fig. 4 is a perspective view of the commutator of the motor, showing the formation of electrical connections between the armature coil and the commutator by a fusion method.

Referring to Fig. 1, an immersed-motor fuel pump 1 generally comprises a pump mechanism 2 and an electric motor 3. The motor 3 is completely housed inside a casing 5. Between the motor 3 and the casing 5 is defined a motor chamber 4 which is filled with fuel and forms a part of the fuel conveyance path. The motor 3 has a driving shaft 11 which is rotatably supported by a pair of bearings 12, 1 2. An armature core 1 3 is fixedly mounted on the driving shaft 11 and an armature coil 14 is wound around the armature core 13.

The driving shaft 11 carries a commutator 1 6 which comprises a plurality of segments electrically insulated from one another. A pair of brushes 1 7 is provided, each in sliding contact with the outer peripheral surface of the commutator 1 6. Each of the brushes 1 7 is slidably supported by a brush holder 18 and is normally pressed against the commutator 1 6 by means of a spring. A pair of brush leads 1 9 is provided,each having one end implanted in the brush 1 7 and the other end connected to the brush holder 1 8. A pair of terminal leads 20 is provided, each having one end connected to the brush holder 1 8 and the other end connected to a terminal connector 22.

Each terminal lead includes a coil 21 between its ends. Electrical connection to an external source (not shown) is made through the connector 22, thereby supplying electric power to the motor 3. A magnet holder 23 holds a plurality of field magnets (not shown) and a damper 24 is provided to absorb pressure fluctuations in the flow of fuel.

The pump mechanism 2 shown in the drawing is a vane pump, the details of which are shown in Fig. 3, The vane pump 2 comprises a housing 31 and a rotor 33 disposed inside the housing 31, the rotor 33 being fixedly mounted on the driving shaft 11 at one end thereof. A plurality of recesses 35 is provided along the periphery of the rotor 33 and a roller vane 34 is movably inserted in each of the recesses 35. A pump chamber 38 is defined between the rotor 33 and the housing 31. The rotation of the rotor 33 brings fuel into the pump chamber 38 through a pump inlet port 39 and conveys the tuel into the motor cnamDer 4 through a pump outlet port 40.Accordingly, when the pump 2 is driven by the motor 3, the flow of fuel as shown by the arrows in Fig. 1 is formed the fuel being introduced into the motor chamber 4 through an inlet nipple 41 and discharged through an outiet port 42. As is apparent, the motor 3 is cooled during operation s;nce the heat generated within the motor 3 is carried away by the flow of fuel; moreover, sparks between the commutator 1 6 and the brushes 1 7 are suppressed, and the possibility of induced explosions of vaporized fuel due to these sparks is precluded.

Some components of the motor-immersed fuel pump are made from a material, such a aluminium, which does not contain copper so as not to degrade petrol fuel. However, some components still require to be made from copper or copper alloy in order to maintain economical advantage without lowering the motor performance. Typically, these components are the armature coil 14, commutator segments 1 6 and various leads 1 9, 20 and 21. As regards the armature coil 14, since it is relatively long, the electrical conductivity of a material used is a very important factor. Thus, in order to maintain a high motor performance without unduiy increasing the manufacturing cost, one is obliged to use copper wire as an armature coil.

As regards the commutator 6, if each segment is made from copper or copper alloy, a protective layer is formed by electro-plating onto the surface of each segment silver or any other material which has a high electrical conductivity and which is non-reactive with petrol. However, the commutator 6 is subjected to the abrasive action of the brushes 1 7. So, in order to increase the mechanicai durability, a silver sheet material 1 6a of 0.4 to 1.2mm thick may be fixedly provided on the surface of a copper commutator segment 1 6b.

Therefore, even if the commutator 16 is excessively rubbed by the brushes 17, the copper portions will not be exposed.

The brush leads 1 9 may be made from a material which is not reactive with petrol such as tin, nickel, silver, silver alloy, stainless steel, or aluminium. If copper wire is used for the brush leads 1 9 as a trade-off between electrical and economical advantages, a protective cover layer is formed on the copper wire. A nickel electro-plated layer of 2 to 6 microns thick is useful as such a protective layer. The similar concept holds true with respect to the terminal leads 20 and 21.

As regards the armature coil 14, use may be made of copper wire coated with an insulating material such as enamel. As it is, the copper wire does not come into direct contact with the fuel, except at its ends, when immersed in the fuel.

However, a probiem arises when such an enamelcoated copper wire is connected to the commutator 1 6 during the manufacturing process.

That is to say, when the connection 1 4a between the armature coil and the commutator is formed, such method as soldering, silver-soldering, and fusing is employed to ensure good electrical conduction throughout the connection 14a. Since a significant amount of heat is applied by these methods, the coating material is partly melted away to expose the copper wire.

Referring to Fig. 4, explanation will be given to the formation of connection 1 4a between the coil wire 1 4b and the commutator 1 6. Fig. 4 illustrates the technique, called fusing, to form the connection 1 4a under pressure and heating by electric current. The coil wire 1 4b is brought into engagement with a hook 1 6c formed at one end of each segment of the commutator 1 6. A first electrode 51 is lowered and pressed against the hook 16c. At the same time, a second electrode 52 is brought to an appropriate position to be in contact with the commutator segment with which the first electrode 51 is also in contact.Then, the first and the second electrodes are connected to a d.c. or a.c. high voltage source (not shown) for a certain period of time to draw a current of certain intensity between the electrodes. Since the coil wire 1 4b is pinched in the hook 1 6c under pressure, there is a high electrical resistance between them and, therefore, a significant amount of heat is produced by passing a current therebetween. As a result, the portions which are in contact under pressure become melted and integrated into the same body when cooled.

However, since copper is a good thermal conductor, the heat quickly dissipates along the coil wire 1 4b and the coating material is removed over a distance 1 by melting. When the fusing technique was applied it was found that this distance 1 falls at least in the range of 3 to 4mm.

Therefore, upon formation of the connection between the coil wire and the commutator, it is necessary to provide a protective layer of a material non-reactive with petrol at least in the neighbourhood of the connection 14a, in particular over an intended distance along the coil wire from the connection 14a. For this purpose, an organic adhesive material, such as epoxy resin, may be used to form such protective layer by brushing or spraying. So far, explanation has been given where the connection is formed by a fusing technique. It should be easily understood, however, that the similar concept is applicable where the connection is formed by soldering or silver-soldering.

It will be understood that various changes in details, materials, and arrangements of parts, which have been herein described and illustrated in order to explain the nature of the invention, may be made by those skilled in the art within the scope of the invention. However, while the invention has been described with reference to the structure illustrated in the drawings, it is not to be confined to the details set forth, and this application is intended to cover such modifications or changes as may come within the scope of the

Claims (12)

claims. CLAIMS

1. A fuel pump comprising a motor having casing around the inner surface of which is disposed a plurality of magnets, an armature disposed inside said casing and a driving shaft rotatably supported in the pump and carrying said armature and a commutator, and a pump mechanism driven by said driving shaft and disposed so that the flow path of the pumped fuel is through the casing, the armature thereby being completely immersed in the fuel, the armature coil of said armature comprising a copper wire and a protective layer provided to cover said copper wire, said protective layer being made from a material non-reactive with fuel.

2. A fuel pump as claimed in claim 1 ,further including a secondary protective layer of a material non-reactive with fuel provided at least in the neighbourhood of the connection between the armature coil and the commutator, said secondary protective layer being formed after the formation of said connection.

3. A fuel pump as claimed in claim 2, wherein said secondary protective layer is provided over an intended distance along the armature coil from said connection.

4. A fuel pump as claimed in claim 2 or 3, wherein the material or said secondary protective layer is an organic adhesive material.

5. A fuel pump as claimed in claim 4 wherein said organic adhesive material is an epoxy resin.

6. A fuel pump as claimed in any preceding claim, wherein the commutator comprises a plurality of copper segments, each segment being covered with a protective layer of a material nonreactive with fuel.

7. A fuel pump as claimed in claim 6, wherein the material of the protective layer for said armature coil is an insuiating material and the protective layer for said commutator segments is an electroplated layer of silver or silver alloy.

8. A fuel pump as claimed in claim 6 or 7, further including a copper brush lead which is covered with a protective layer of a material nonreactive with fuel.

9. A fuel pump as claimed in claim 8, further including a copper terminal lead which is covered with a protective layer of a material non-reactive with fuel.

10. A fuel pump as claimed in any preceding claim, wherein said fuel is petrol.

11. A fuel pump as claimed in claim 10 wherein the petrol has alcohol added thereto.

12. A fuel pump constructed substantially as herein described with reference to and as illustrated in the drawings.